If you are planning to buy a pendrive to use with your smartphone do check out the Sandisk Ultra Dual pendrive that can be used on a computer as well as a smartphone. You don’t need an OTG cable just plug in the micro USB connector into the smartphones micro USB port.
With limited storage space on a smartphone, pendrive are now being used as an alternate storage option along with the Micro SD cards ( some phones come without micro SD option). To use a pendrive your smartphone should support OTG. Now if you already have a pendrive with USB 2.0 connector (i.e. with standard USB connector) you can buy the OTG cable and use your existing pendrive.
But in case if you are planning to get a new one especially to use with the Smartphone you should consider buying the dual pendrives available in the market. The Sandisk Ultra Dual is one such device that comes with a USB 2.0 (normal) connection and a micro USB connector. Build quality is good made of plastic and both the connectors has slide in/out plastic protection.
This is just like any other ordinary pendrive, except that it comes with built in OTG support. There is no difference in the drive performance as compared with the other USB 2.0 pendrives.
The best thing about the dual pendrive is that there is no messy cable around (the OTG cable). The drive is compact and sticks well with the smartphone though it is not that slim. Read Speed = 19.69MB/s and Write speed = 11.91MB/s.